Journal of Ultrasound in Medicine, Vol 19, Issue 1 7-12, Copyright © 2000 by American Institute of Ultrasound in Medicine
Predictive value of sonographic examination to visualize retained placenta directly after birth at 16 to 28 weeks
J. I. de Vries, R. M. van der Linden and H. C. van der Linden
Department of Obstetrics and Gynaecology, Free University Hospital, Amsterdam, The Netherlands.
A prospective study was performed to assess the predictive value of an
ultrasonographic examination directly after a spontaneous birth at 16 to 28
weeks' gestation to exclude the possibility of retained placental tissue.
The aim of this procedure is to prevent routine curettage, which can induce
Asherman's syndrome, uterine perforation, and anesthetic complications.
Over a 2 year period the clinical course in 64 women, who had been
delivered of their infants at 16 to 28 weeks' gestation, was followed
through 6 weeks post partum. Sonographic examination was performed within
30 min after delivery of the placenta independent of macroscopic judgment
of completeness of placenta. The examination was classified into three
categories (with subsequent clinical interpretation): sharp lining of
echogenic uterine wall with translucent cavity (uterine cavity containing
fluid blood), sharp lining of the wall with echogenic area in cavity not
continuous with the wall (uterine cavity with blood clot), and irregular
lining with echogenic area continuous with the uterine wall and extending
into the cavity (uterine cavity containing retained placental tissue).
Women with sharp uterine lining without (n = 32) or with (n = 7)
echogenicity in the cavity had no direct operative removal of placental
tissue; 3 underwent curettage at a later stage (17, 18, and 34 days,
respectively). A direct digital removal of placenta or curettage was
performed on 25 women who revealed echogenicity continuous with the uterine
wall. The 25 of 28 operatively obtained tissues were examined
microscopically for trophoblasts. The sensitivity of the sonographic
examination to find retained placental tissue was 85% (17 of 20) at 95%
confidence intervals of 62 to 97%, the specificity was 88% (36 of 41) at
95% confidence intervals of 74 to 96%, and there were 25% (5 of 20) false
positive judgments and 8% (3 of 39) false negative judgments. The positive
predictive value of ultrasonography to find retained placenta of 68% (17 of
22) at 95% confidence interval of 55 to 92% combined with the negative
predictive value of 92% (36 of 39) is sufficient to strongly suggest that
curettage should not be performed routinely in these pregnancies at high
risk for retained placental tissue.
